Traps enable interrupts conditionally but rely on the ASM return code to disable them again. That results in redundant interrupt disable and trace calls.
Make the trap handlers disable interrupts before returning to avoid that, which allows simplification of the ASM entry code. Originally-by: Peter Zijlstra <pet...@infradead.org> Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- arch/x86/kernel/traps.c | 28 +++++++++++++++++++--------- arch/x86/mm/fault.c | 15 +++++++++++++-- 2 files changed, 32 insertions(+), 11 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -201,6 +201,7 @@ static void do_error_trap(struct pt_regs NOTIFY_STOP) { cond_local_irq_enable(regs); do_trap(trapnr, signr, str, regs, error_code, sicode, addr); + cond_local_irq_disable(regs); } } @@ -399,6 +400,8 @@ dotraplinkage void do_bounds(struct pt_r die("bounds", regs, error_code); do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, 0, NULL); + + cond_local_irq_disable(regs); } enum kernel_gp_hint { @@ -458,12 +461,13 @@ dotraplinkage void do_general_protection if (static_cpu_has(X86_FEATURE_UMIP)) { if (user_mode(regs) && fixup_umip_exception(regs)) - return; + goto exit; } if (v8086_mode(regs)) { local_irq_enable(); handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code); + local_irq_disable(); return; } @@ -475,12 +479,11 @@ dotraplinkage void do_general_protection show_signal(tsk, SIGSEGV, "", desc, regs, error_code); force_sig(SIGSEGV); - - return; + goto exit; } if (fixup_exception(regs, X86_TRAP_GP, error_code, 0)) - return; + goto exit; tsk->thread.error_code = error_code; tsk->thread.trap_nr = X86_TRAP_GP; @@ -492,11 +495,11 @@ dotraplinkage void do_general_protection if (!preemptible() && kprobe_running() && kprobe_fault_handler(regs, X86_TRAP_GP)) - return; + goto exit; ret = notify_die(DIE_GPF, desc, regs, error_code, X86_TRAP_GP, SIGSEGV); if (ret == NOTIFY_STOP) - return; + goto exit; if (error_code) snprintf(desc, sizeof(desc), "segment-related " GPFSTR); @@ -518,6 +521,8 @@ dotraplinkage void do_general_protection die_addr(desc, regs, error_code, gp_addr); +exit: + cond_local_irq_disable(regs); } NOKPROBE_SYMBOL(do_general_protection); @@ -775,7 +780,7 @@ static void math_error(struct pt_regs *r if (!user_mode(regs)) { if (fixup_exception(regs, trapnr, error_code, 0)) - return; + goto exit; task->thread.error_code = error_code; task->thread.trap_nr = trapnr; @@ -783,7 +788,7 @@ static void math_error(struct pt_regs *r if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) != NOTIFY_STOP) die(str, regs, error_code); - return; + goto exit; } /* @@ -797,10 +802,12 @@ static void math_error(struct pt_regs *r si_code = fpu__exception_code(fpu, trapnr); /* Retry when we get spurious exceptions: */ if (!si_code) - return; + goto exit; force_sig_fault(SIGFPE, si_code, (void __user *)uprobe_get_trap_addr(regs)); +exit: + cond_local_irq_disable(regs); } dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code) @@ -855,6 +862,8 @@ do_device_not_available(struct pt_regs * info.regs = regs; math_emulate(&info); + + cond_local_irq_disable(regs); return; } #endif @@ -885,6 +894,7 @@ dotraplinkage void do_iret_error(struct do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code, ILL_BADSTK, (void __user *)NULL); } + local_irq_disable(); } #endif --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -927,6 +927,8 @@ static void force_sig_fault(SIGSEGV, si_code, (void __user *)address); + local_irq_disable(); + return; } @@ -1548,9 +1550,18 @@ do_page_fault(struct pt_regs *regs, unsi return; /* Was the fault on kernel-controlled part of the address space? */ - if (unlikely(fault_in_kernel_space(address))) + if (unlikely(fault_in_kernel_space(address))) { do_kern_addr_fault(regs, hw_error_code, address); - else + } else { do_user_addr_fault(regs, hw_error_code, address); + /* + * User address page fault handling might have reenabled + * interrupts. Fixing up all potential exit points of + * do_user_addr_fault() and its leaf functions is just not + * doable w/o creating an unholy mess or turning the code + * upside down. + */ + local_irq_disable(); + } } NOKPROBE_SYMBOL(do_page_fault);